This invention generally relates to television and more particularly apparatus and methods for selectively providing video input signals to television from a plurality of different television signal sources.
Users of televisions today often have available to them multiple sources of televisions signals which they wish to couple to a single television or television monitor for selective using. Such sources include commercial cable television sources, cable security camera sources, local network broadcast television sources received via land based antennas and more recently direct broadcast satellite sources received via satellite dish antennas.
Reception of commercial cable television signals are sent in coded format and must be decoded by converter circuits or so-called converter boxes. These converter boxes contain circuits which selectively tune in different source channels in response to direct or remote selection by the user. The channel numbers associated with the different channels are pre-established by the cable television service provider and cannot be altered or programmed by the user. However, such converter boxes are known to have the ability to allow on-screen program preselection of so-called "favorite channels" which are less in number than the total number of available channels. Operation of a favorite channel button switch on the remote control unit causes a channel selector to scan only the preselected favorite channels while skipping over the other channels.
Likewise, direct broadcast satellite, or DBS, television signals received at a user satellite dish antenna must be decoded and selectively tuned into the selected channels and such DBS systems employ a converter box like that employed with the cable television service providers. Like in cable television service, the direct broadcast satellite television service providers preselect which channel numbers displayed on the converter box correspond to which source channels or stations and these preselections cannot be changed by the user or viewer.
Other sources of television input signals do not require decoding, such as land based local network public broadcast signals, also have preselected channels assigned to them by the Federal Communication Commission, or FCC. Although cable decoders are known to provide tuners that are adjustable with respect to the displayed channel assigned to any given public broadcast network channel, employing a user channel number for a public broadcasting channel which is different than the network channel number is confusing and to be avoided.
It is also sometimes desired to couple other cable sources, such as television security cameras, other internal programming cable sources, or the like.
Many televisions have only one antenna, or "video in", input terminal, and in order for the converter boxes to control tuning, the television is tuned to a particular open channel on which local public broadcast stations do not broadcast and are not received, such as channel-3 and channel-4, on which all the cable channels signals are modulated.
Problems or difficulties develop when it is desired to convert multiple television sources to a single television monitor. For instance, due to FCC Regulations, direct broadcast satellite services are not permitted to include as part of their service local network programming such as local programming from CBS, NBC and ABC affiliates. A user of direct broadcast satellite television services must employ a separate mechanical switch box, employ a switch box built into a converter box or physically switch cable inputs to their television in order to change between a local public broadcast network program and programming on the direct broadcast satellite channels. In any event, the input is connected to the local public broadcast, the tuner of the television must be used to tune in the public broadcast stations.